DC-DC converters, as an example of power converters, are often used in electronic devices, electronic systems, and the like. DC-DC converters normally use switching elements and an inductor, such as a transformer, and perform on-off control of the switching elements to convert, via the switching elements and inductor, input DC power into output DC power different from the input DC power.
Such DC-DC converters perform feedback control that measures a value of the output DC power via a feedback loop, and compares a command value for the output DC power with the measured value of the output DC power, thus determining a manipulated variable for each of the switching elements based on results of the comparison.
These DC-DC converters are classified broadly into voltage-mode control DC-DC converters and current-mode control DC-DC converters. A voltage-mode control DC-DC converter is designed to perform on-off control of the switching elements using a voltage feedback loop of its output voltage. In contrast, a current-mode DC-DC converter is designed to perform on-off control of the switching elements using the combination of the voltage feedback loop and a current feedback loop of a current flowing through the inductor as an inductor current.
In these current-mode DC-DC converters, there have been disclosed some technologies for reducing the variation in the output voltage even when the output current flowing through a load rapidly changes. One example of these technologies is disclosed in Japanese Patent Application Publication No. 2002-281742.
The current-mode DC-DC converter disclosed in the Patent Publication measures a value of an inductor current flowing through the inductor using the current feedback loop. Then, the current-mode control DC-DC converter compares the measured value of the inductor current with a command current value determined based on a command voltage for the output voltage thereof, thus performing on-off control of the switching elements according to results of the comparison. This adjusts the output voltage of the current-mode control DC-DC converter to the command voltage.
Particularly, the current-mode control DC-DC converter disclosed in the Patent Publication is equipped with a feedforward circuit that measures a change in an output current flowing through a load. The feedforward circuit adds the detected change to a corresponding measured value of the inductor current, thus correcting the measured value of the inductor current to follow the change in the output current flowing through the load.